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[texts]String Theory - J. L. F. Barbon
This is a rendering of a review talk on the state of String Theory, given at the EPS-2003 Conference, intended for a wide audience of experimental and theoretical physicists. It emphasizes general ideas rather than technical aspects.
Downloads: 68 4.00 out of 5 stars4.00 out of 5 stars4.00 out of 5 stars4.00 out of 5 stars(1 review)
[texts]Causal set as a discretized phase spacetime - Roman Sverdlov
The first goal of this paper is to show that discreteness, locality, and relativistic covariance can peacefully coexist if the ordinary spacetime (OST) is replaced with phase spacetime (PST) as a geometric background of a Poisson process, where PST is a spacetime generalization of a notion of phase space (this is a 7-dimensional version of the 8-dimensional structure proposed by Caianiello). Furthermore, Caianiello's idea of finite acceleration is implemented...
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[texts]Chronon corrections to the Dirac equation - Andrei A. Galiautdinov
The Dirac equation is not semisimple. We therefore regard it as a contraction of a simpler decontracted theory. The decontracted theory is necessarily purely algebraic and non-local. In one simple model the algebra is a Clifford algebra with 6N generators. The quantum imaginary $\hbar i$ is the contraction of a dynamical variable whose back-reaction provides the Dirac mass. The simplified Dirac equation is exactly Lorentz invariant but its symmetry group is SO(3,3), a decontraction of the Poinca...
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[texts]Sign reversal of ac Josephson current in a ferromagnetic Josephson junction - S. Hikino
The ac Josephson effect in a ferromagnetic Josephson junction, which is composed of two superconductors separated by a ferromagnetic metal (FM), is studied by a tunneling Hamiltonian and Green's function method. We obtain two types of superconducting phase dependent current, i.e., Josephson current and quasiparticle-pair-interference current (QPIC). These currents change their signs with thickness of the FM layer due to the 0-$\pi$ transition characteristic to the ferromagnetic Josephson junctio...
Downloads: 1
[texts]Representing embeddability as set inclusion - Menachem Kojman
A few steps are made towards representation theory of embeddability among uncountable graphs. A monotone class of graphs is defined by forbidding countable subgraphs, related to the graph's end-structure. Using a combinatorial theorem of Shelah it is proved: - The complexity of the class in every regular uncountable $\l>\aleph_1$ is at least $\lambda^+ + \sup\{\mu^{\aleph_0}:\mu^+\aleph_1$ there are $2^\lambda$ pairwise non embeddable graphs in the class having strong homogeneity properties...
[texts]Intrinsic volumes of symmetric cones - Dennis Amelunxen
We compute the intrinsic volumes of the cone of positive semidefinite matrices over the real numbers, over the complex numbers, and over the quaternions, in terms of integrals related to Mehta's integral. Several applications for the probabilistic analysis of semidefinite programming are given.
[texts]Comment on "Multiferroicity Induced by Dislocated Spin-Density Waves" - A. B. Harris
I show that the claims in Phys. Rev. Lett. 98, 257602 by Betouras et al concerning YMn2O5 are incorect.
Downloads: 1
[texts]Exponential-Potential Scalar Field Universes II: The Inhomogeneous Models - J. M. Aguirregabiria
We obtain exact solutions for the Einstein equations with an exponential-potential scalar field (\(V=\Lambda e^{k\phi}\)) which represent simple inhomogeneous generalizations of Bianchi I cosmologies. Studying these equations numerically we find that in most of the cases there is a certain period of inflationary behaviour for \(k^22\) the solutions homogenize generically at late times. Yet, {\em none of the solutions} isotropize...
[texts]Compounding Fields and Their Quantum Equations in the Trigintaduonion Space - Zihua Weng
The 32-dimensional compounding fields and their quantum interplays in the trigintaduonion space can be presented by analogy with octonion and sedenion electromagnetic, gravitational, strong and weak interactions. In the trigintaduonion fields which are associated with the electromagnetic, gravitational, strong and weak interactions, the study deduces some conclusions of field source particles (quarks and leptons) and intermediate particles which are consistent with current some sorts of interact...
[texts]Single-spin asymmetries: the Trento conventions - Alessandro Bacchetta
During the workshop "Transversity: New Developments in Nucleon Spin Structure" (ECT*, Trento, Italy, 14-18 June 2004), a series of recommendations was put forward by the participants concerning definitions and notations for describing effects of intrinsic transverse momentum of partons in semi-inclusive deep inelastic scattering.
[texts]Casimir Invariants for Quantized Affine Lie Algebras - M. D. Gould
Casimir invariants for quantized affine Lie algebras are constructed and their eigenvalues computed in any irreducible highest weight representation.
Downloads: 1
[texts]Calculation of High Energy Neutrino-Nucleon Cross Sections and Uncertainties Using the MSTW Parton Distribution Functions and Implications for Future Experiments - Amy Connolly
We present a new calculation of the cross sections for charged current (CC) and neutral current (NC) $\nu N$ and $\bar{\nu} N$ interactions in the neutrino energy range $10^{4}
Downloads: 4
[texts]G272.2--3.2: A centrally filled and possibly young SNR discovered by ROSAT - J. Greiner
We report the discovery of a new SNR in the \ros All-Sky-Survey data. The SNR has a nearly circular shape with a diameter of about 15 arcmin. The surface brightness is rather uniform over the remnant. The observed interstellar absorption suggests a distance of about 1.8$^{+1.4}_{-0.8}$ kpc. The X-ray emission appears to be of thermal origin with a plasma temperature of about 10$^7$ K. The Sedov model leads to an age of only 1800 years...
[texts]Looking into the hearts of Bok globules: MM and submm continuum images of isolated star-forming cores - R. Launhardt
We present the results of a comprehensive infrared, submillimetre, and millimetre continuum emission study of isolated low-mass star-forming cores in 32 Bok globules, with the aim to investigate the process of star formation in these regions. The submillimetre and millimetre dust continuum emission maps together with the spectral energy distributions are used to model and derive the physical properties of the star-forming cores, such as luminosities, sizes, masses, densities, etc...
Downloads: 3
[texts]Chiral symmetry and many-body nonleptonic decays of bottom hadrons - Q. P. Xu
Chiral symmetry can be applied to many-body nonleptonic decays of heavy hadrons. We establish the chiral effective Hamiltonian for some typical many-body nonleptonic decays of bottom hadrons. We discuss the lowest-order contributions coming from such a Hamiltonian and present, as an example, a calculation of decay distributions of $B^-\to D^+ D^-_s \pi^-$ and $B^-\to D^{\ast +} D^-_s \pi^-$. We emphasize that wide applications of this method are possible.
Downloads: 1
[texts]Study of temperature dependent atomic correlations in MgB$_{2}$ - G. Campi
We have studied the evolution with temperature of the local as well as the average crystal structure of MgB$_2$ using the real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction. We have investigated the correlations of the B-B and B-Mg nearest neighbor pair motion by comparing, in the wide temperature range from T=10 K up to T=600 K, the mean-square displacements (MSD) of single atoms with the mean-square relative displacements (MSRD) obtained f...
[texts]Single-electron Tunneling with Strong Mechanical Feedback - Ya. M. Blanter
We show that there is a regime of strong feedback for a nanomechanical oscillatory mode weakly coupled to a single-electron tunneling device. In this regime, the current is strongly modified whereas the current noise is parametrically big exceeding the Schottky limit by orders of magnitude. This regime requires a high quality factor of nanomechanical oscillations.
Downloads: 2
[texts]Monte Carlo simulations of Sznajd models - Dietrich Stauffer
The Sznajd model in less than a year has found several followers. An isolated person does not convince others; a group of people sharing the same opinions influences the neighbours much more easily. Thus on a square lattice, with variables +1 (Democrats) and --1 (Republicans) on every lattice site, a pair (or plaquette) of neighbours convinces its six (eight) nearest neighbours of its own opinion if and only if all members of the pair (plaquette) share the same opinion...
[texts]Ghost Poles in the Nucleon Propagator: Vertex Corrections and Form Factors - G. Krein
Vertex corrections are taken into account in the Schwinger-Dyson equation for the nucleon propagator in a relativistic field theory of fermions and mesons. The usual Hartree-Fock approximation for the nucleon propagator is known to produce the appearance of complex (ghost) poles which violate basic theorems of quantum field theory. In a theory with vector mesons there are vertex corrections that produce a strongly damped vertex function in the ultraviolet...
[texts]Be careful with the Exp-function method - Nikolay A. Kudryashov
An application of the Exp-function method to search for exact solutions of nonlinear differential equations is analyzed. Typical mistakes of application of the Exp-function method are demonstrated. We show it is often required to simplify the exact solutions obtained. Possibilities of the Exp-function method and other approaches in mathematical physics are discussed. The application of the singular manifold method for finding exact solutions of the Fitzhugh - Nagumo equation is illustrated...
Downloads: 2
[texts]Anomalous Negative Magnetoresistance Caused by Non-Markovian Effects - Vadim V. Cheianov
A theory of recently discovered anomalous low-field magnetoresistance is developed for the system of two-dimensional electrons scattered by hard disks of radius $a,$ randomly distributed with concentration $n.$ For small magnetic fields the magentoresistance is found to be parabolic and inversely proportional to the gas parameter, $ \delta \rho_{xx}/\rho \sim - (\omega_c \tau)^2 / n a^2.$ With increasing field the magnetoresistance becomes linear $\delta \rho_{xx}/\rho \sim - \omega_c \tau $ in ...
[texts]Shrinking and the True Power Spectrum at Decoupling - B. A. C. C. Bassett
In this paper we examine the change in the estimated spatial power spectra at decoupling due to the effects of our clumpy universe which modify observational distances. We find that scales at decoupling can be significantly underestmated in our approximation of neglecting the shear of the ray bundle. We compare our results with other work on lensing and speculate on the implications for structure formation...
[texts]Propositional Manifolds - Joseph Kouneiher
This paper was withdrawn by the author due to an edition's rights
Downloads: 2
[texts]The Langevin equation from Markovian Quantum Central Limits - John Gough
This paper has been withdrawn by the author. The central result is now included in quant-ph/0309056 (as in the journal publication!). An erratum on the Heisenberg perturbation series estimate is also included therein.
Downloads: 2
[texts]A few brief comments to arXiv:1005.3315 and arXiv:1005.3321 - V. Gogokhia
It is discussed the inconsistency of the so-called ladder-rainbow truncation scheme to QCD in the framework of the Dyson-Schwinger equation for the quark propagator and the Bethe-Salpeter equation for the bound state of mesons.
Downloads: 2
[texts]Comment on ``Critical branching captures activity in living neural networks and maximizes the number of metastable states'' - Dietmar Plenz
It is shown that, contrary to the claims in a recent letter by Haldeman and Beggs (PRL, 94, 058101, 2005), the branching ratio in epileptic cortical cultures is smaller than one. In addition, and also in contrast to claims made in that paper, the number of metastable states is not significantly different between cortical cultures in the critical state and cultures made epileptic using picrotoxin.
[texts]A posteriori teleportation - Samuel L. Braunstein
The article by Bouwmeester et al. on experimental quantum teleportation constitutes an important advance in the burgeoning field of quantum information. The experiment was motivated by the proposal of Bennett et al. in which an unknown quantum state is `teleported' by Alice to Bob. As illustrated in Fig. 1, in the implementation of this procedure, by Bouwmeester et al., an input quantum state is `disembodied' into quantum and classical components, as in the original protocol...
[texts]Shape oscillation of bubbles in the acoustic field - Keishi Matsumoto
The authors introduce dynamics of multiple air bubbles exposed to ultrasonic wave while ascending in water in the present fluid dynamics video. The authors pay attention to the shape oscillation and the transition from the volume to the shape oscillations of the bubble. Correlation between the bubble size and the mechanism of the excitation of the shape oscillation is introduced.
Downloads: 2
[texts]Symmetries of the Robinson-Trautman equation - Wlodzimierz Natorf
We study point symmetries of the Robinson--Trautman equation. The cases of one- and two-dimensional algebras of infinitesimal symmetries are discussed in detail. The corresponding symmetry reductions of the equation are given. Higher dimensional symmetries are shortly discussed. It turns out that all known exact solutions of the Robinson--Trautman equation are symmetric.
Downloads: 2
[texts]Symmetry-adapted algebraic description of stretching and bending vibrations of ozone - F. Perez-Bernal
The vibrational excitations of ozone, including both bending and stretching vibrations, are studied in the framework of a symmetry-adapted algebraic approach. This method is based on the isomorphism between the U(2) algebra and the one-dimensional Morse oscillator, and the introduction of point group symmetry techniques. The use of symmetry-adapted interactions, which in the harmonic limit have a clear physical interpretation, makes it possible to systematically include higher order terms and an...
Downloads: 1
[texts]Comments on "Stability of Tsallis entropy and instabilities of Renyi and normalized Tsallis entropies: A basis for q-exponential distributions" - Andrei G. Bashkirov
It is shown that the Renyi entropy is as stable as the Tsallis entropy at least for Abe-Lesche counterexamples.
[texts]Phase Ordering in One-Dimensional Systems with Long-Range Interactions - B. P. Lee
We study the dynamics of phase ordering of a non-conserved, scalar order parameter in one dimension, with long-range interactions characterized by a power law $r^{-d-\sigma}$. In contrast to higher dimensional systems, the point nature of the defects allows simpler analytic and numerical methods. We find that, at least for $\sigma > 1$, the model exhibits evolution to a self-similar state characterized by a length scale which grows with time as $t^{1/(1+\sigma)}$, and that the late time dynamics...
Downloads: 1
[texts]Early stages of the shear banding instability in wormlike micelles - Suzanne M. Fielding
We study the early stages of the shear banding instability in semidilute wormlike micelles using the non-local Johnson-Segalman model with a two-fluid coupling of the concentration (phi) to the shear rate (gamma_dot) and micellar strain (tensor{W}). We calculate the ``spinodal'' limit of stability for sweeps along the homogeneous intrinsic flow curve. For startup ``quenches'' into the unstable region, the instability in general occurs before the homogeneous startup flow can attain the intrinsic ...
Downloads: 1
[texts]On the Farrell-Jones Conjecture and its applications - Arthur Bartels
We present the status of the Farrell-Jones Conjecture for algebraic K-theory for a group G and arbitrary coefficient rings R. We add new groups for which the conjecture is known to be true and study inheritance properties. We discuss new applications, focussing on the Bass Conjecture, the Kaplansky Conjecture and conjectures generalizing Moody's Induction Theorem. Thus we extend the class of groups for which these conjectures are known considerably.
[texts]The discovery of a molecular cavity in the Norma near arm associated to H.E.S.S gamma-ray source located in the direction of Westerlund 1 - A. Luna
We report on the discovery of a molecular cavity in the Norma near arm in the general direction of Westerlund 1 (Wd1), but not associated with it. The cavity has a mean radial velocity of -91.5 kms^{-1}, which differs by as much as ~40 kms^{-1} from the mean radial velocity of the Wd1 stars. The cavity is surrounded by a fragmented molecular shell of an outer diameter of about 100 pc and 10^{6} M_odot, which is expanding at velocities of 6 to 8 kms^{-1}...
[texts]LinkRank: Finding communities in directed networks - Youngdo Kim
To identify communities in directed networks, we propose a generalized form of modularity in directed networks by introducing a new quantity LinkRank, which can be considered as the PageRank of links. This generalization is consistent with the original modularity in undirected networks and the modularity optimization methods developed for undirected networks can be directly applied to directed networks by optimizing our new modularity...
Downloads: 3
[texts]Quark spectral properties above Tc from Dyson-Schwinger equations - Jens A. Mueller
We report on an analysis of the quark spectral representation at finite temperatures based on the quark propagator determined from its Dyson-Schwinger equation in Landau gauge. In Euclidean space we achieve nice agreement with recent results from quenched lattice QCD. We find different analytical properties of the quark propagator below and above the deconfinement transition. Using a variety of ansaetze for the spectral function we then analyze the possible quasiparticle spectrum, in particular ...
[texts]A comment on: `Some problems with calculating the quantum corrections to the classical 't Hooft-Polyakov monopole' - Nathan F. Lepora
In a recent publication we noticed that the Hamiltonian density for fluctuations around the 't Hooft-Polyakov monopole appeared to be non-Hermitian. Here we show that when this Hamiltonian density is integrated into the Hamiltonian all non-Hermitian terms give a vanishing total contribution.
[texts]Superconductivity at 32 K in single crystal Rb$_{0.78}$Fe$_2$Se$_{1.78}$} - A. F. Wang
We successfully grew the high-quality single crystal of Rb$_{0.78}$Fe$_2$Se$_{1.78}$, which shows sharp superconducting transition in magnetic susceptibility and electrical resistivity. Resistivity measurements show the onset superconducting transition ($T_{\rm c}$) at 32.1 K and zero resistivity at 30 K. From the low-temperature iso-magnetic-field magnetoresistance, large upper critical field $H_{\rm c2}$(0) has been estimated as high as 180 T for in-plane field and 59 T for out-of-plane field...
Downloads: 2
[texts]Examples of Embedded Defects (in Particle Physics and Condensed Matter) - Nathan F. Lepora
We present a series of examples designed to clarify the formalism of the companion paper `Embedded Vortices'. After summarising this formalism in a prescriptive sense, we run through several examples: firstly, deriving the embedded defect spectrum for Weinberg-Salam theory, then discussing several examples designed to illustrate facets of the formalism. We then calculate the embedded defect spectrum for three physical Grand Unified Theories and conclude with a discussion of vortices formed in th...
[texts]New expression for the K-shell ionization - J. P. Santos
A new expression for the total K-shell ionization cross section by electron impact based on the relativistic extension of the binary encounter Bethe (RBEB) model, valid from ionization threshold up to relativistic energies, is proposed. The new MRBEB expression is used to calculate the K-shell ionization cross sections by electron impact for the selenium atom. Comparison with all, to our knowledge, available experimental data shows good agreement.
Downloads: 1
[texts]Superconducting Upper Critical Field Near a 2D Van Hove Singularity - R. G. Dias
The superconducting upper critical field $H_{c2}(T)$ of a two dimensional BCS superconductor is calculated in the vicinity of a van-Hove singularity. The zero temperature upper critical field is strongly enhanced at weak coupling when the Fermi contour coincides with van-Hove points, scaling as $H_{c2}(0) \propto T_c^{\sqrt{2}}$ compared to the usual result $H_{c2}(0) \propto T_c^{2}$. The result can be interpreted in terms of the non-Fermi liquid decay of normal state pair correlations in the v...
[texts]Comment on `Ising Pyrochlore Magnets: Low Temperature Properties, ``Ice Rules,'' and Beyond' by R. Siddharthan et al., Phys. Rev. Lett. 83, 1854 (1999) - B. C. den Hertog
In this Comment we argue that Ho$_2$Ti$_2$O$_7$ does not exhibit a transition to a partially ordered state unlike what is argued in PRL 83, 1854 (1999), that it exhibits spin ice behavior, and that the experimental specific heat data by Siddharthan et al. can be accounted for in terms of a "dipolar spin ice" model by including an expected contibution from the nuclear Ho spins to the appropriate long-range treatment of the dipole-dipole interactions.
[texts]Erratum: Dynamics of the Bounds of Squared Concurrence [Phys. Rev. A 79, 032306 (2009)] - Zhao Liu
This is an erratum to our paper.
Downloads: 3
[texts]Scattering of elastic waves by elastic spheres in a NaCl-type phononic crystal - Huanyang Chen
Based on the formalism developed by Psarobas et al [Phys. Rev. B 62, 278(2000)], which using the multiple scattering theory to calculate properties of simple phononic crystals, we propose a very simple method to study the NaCl-type phononic crystal. The NaCl-type phononic crystal consists of two kinds of non-overlapping elastic spheres with different mass densities, $L\acute{a}me$ coefficients and radius following the same periodicity of the ions in the real NaCl crystal...
[texts]Ando, Lavrov, and Segawa Reply - Yoichi Ando
Authors' Reply to the Comment by Janossy et al. [cond-mat/0005275] on our article, "Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x}: Fingerprints of Charged Stripes" [cond-mat/9905071, Phys. Rev. Lett. 83, 2813 (1999)].
[texts]The Counterintuitive Universe - B. G. Sidharth
The major advances in physics have been through counterintuitive breakthroughs-- ideas that seemed to go against prevailing convictions. In the twentieth century the Special and General Theory of Relativity and Quantum Mechanics have provided very good examples of this process. However, twentieth century physics has led to an impasse, one of the most important unsolved problems being the unification of gravitation with other interactions...
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